1. Field of the Invention
The invention relates to band-shaped electrical layer resistance elements and the like and somewhat more specifically to a method of producing such elements.
2. Prior Art
Layer-type resistance elements having resistance layers composed of a metal or a metal alloy exhibit various advantages over the somewhat more conventional carbon layer resistance elements. For example, metal layer resistance elements exhibit a better long-term stability and have a smaller temperature coefficient.
Preferred methods of producing such metal layer resistance elements were based on metal vapor deposition or metal particle dusting of a substrate under high vacuum conditions. In addition, methods are known wherein aqueous or non-aqueous solutions are utilized to produce such metal layer resistance elements. The prior art processes involving the use of vacuum are very expensive because of the substantial amount of equipment which is required to practice such processes. On the other hand, the prior art processes involving deposition or precipitation from metal-containing solutions fail to provide sufficient dispersion and layer thickness control so that accurately reproducible results are very difficult to obtain.
It has heretofore been suggested to form metal layer resistance elements of a desired composition from a mixture of thermally decomposable heavy metal compounds such as, for example, carbonyls, acetylacetones, cyclopentadienes, alkyls, etc. by thermal or pyrolytic decomposition of such organo metallic compounds so that the metal is deposited in a select pattern on a substrate. In comparison to deposition from a liquid, deposition from a gas has the advantage that by suitable selection of a decomposition temperature, the composition of the deposited layer can be precisely controlled by the composition of the gas. In contrast, deposition from a liquid yields a layer having a composition dependent not only on the concentration ratios of material in the liquid but also on the different decomposition energies or decomposition potentials, respectively. Deposition from a gas has the further advantage that the deposition rate and thus the layer thickness can be precisely controlled. A similar advantage may be achieved by deposition from a liquid only if the deposition is limited to a locally restricted highly heated substrate area with all of the desired layer compounds thereat or if such deposition includes an intermediate step of drying the liquid to form a film on the substrate and then heating localized areas of such film to the decomposition temperature of the metal compound within the film. In deposition from a gas, select heavy metal compounds are volatilized and transported to the deposition site by a suitable organic or inorganic carrier gas and/or by means of a reduced or sub-atmospheric pressure.